1. Technical Field
The present invention relates generally to an inspection system, and more particularly, to an engine bearing inspection system and to a method to inspect engine bearings.
2. Description of the Related Art
In motor vehicles, engine bearings serve to withstand the immense mechanical loads generated by crankshaft movement and to protect the crankshaft journals from physically contacting the engine block. Because of the tremendous loads on the inner diameter (ID) surface of these engine bearings, the ID surfaces must remain free from impurities and defects, such as dust, scratches and chips at all times, including during their own manufacturing process. Currently, bearing manufacturers inspect the ID surfaces for defects and impurities with human inspectors. Because of high production demands, manufacturers typically produce eighty bearings every minute. Because of this high throughput, it is not possible for the human inspectors to inspect every bearing for impurities or defects. To increase the numbers of bearings inspected, bearing manufacturers have attempted to inspect the ID surfaces with imaging technology. Conventional inspection approaches have shortcomings.
One approach taken to inspect an inside diameter surface in the context of a can includes using at least three cameras to view the entire ID surface as seen by reference to U.S. Pat. No. 5,699,152 issued to Fedor et al. The expense incurred in using at least three cameras exemplifies an obvious flaw with the approach taken in Fedor et al. Another flaw caused by using multiple cameras (such as in Fedor et al.), in general, involves the generation of internal reflections. Internal reflections are caused by the use of multiple light sources in the imaging process that generate internal reflections, for example within the concave-shaped bearing. The internal reflections, in turn, generate undesirable dark strips on the resulting images of the ID surface. The dark strips will prevent the imaging system from detecting impurities or defects located on these obscured portions of the ID surface images.
Another imaging technology method used to inspect ID surfaces utilizes a single camera. Yet in order to view the bearing in its entirety, either the camera or the bearing under inspection must move to perform a complete scan of the entire surface ID. Moving the bearing slows throughput because extra time must be allotted for the bearing""s motion and the extra movement exposes the bearing to an increased risk of damage. Likewise, moving the camera to scan the bearing also slows throughput because extra time must be allotted for the camera""s motion. Furthermore, in order for the camera to move, the system requires long cables to power and operate the camera. These long cables generate electromagnetic interference that reduces the image quality of the inspection system. Also, the repetitive movement of the camera causes premature wear or breakage of the camera cables. This wear or breakage usually results in the costly replacement of the camera cables.
These disadvantages have made it apparent that a new technique to inspect engine bearings for impurities or defects is needed.
One object of the present invention is to provide a solution to one or more of the above mentioned problems. One advantage of the present invention is that only one camera is needed to acquire the image beam of the inside diameter (ID) surface of a component under inspection such as an engine bearing. Another advantage of the present invention is that the camera remains stationary, thereby eliminating the possibility of excessive wear, breakage and tangling of the camera cables. Another advantage of the present invention is the elimination of internal reflection interference in the resulting image, compared to conventional multi-camera, multi-light source arrangements. Another advantage of the present invention is that the component under inspection remains stationary throughout the scanning process, thus reducing the possibility of damaging the component by excessive movement. Still another advantage of the present invention is that an increased percentage of engine bearings can be inspected for impurities and defects without decreasing throughput.
In one aspect of the invention, an inspection system is provided that is used to view an image of an inside diameter (ID) surface of a component, such as an engine bearing. The system includes a mount, optics, and a line scan camera. The mount is configured to hold the component in a first fixed position during a scanning interval. The optics are configured to direct a source light beam, such as a light line, to the ID surface wherein an image beam is produced. The line scan camera is disposed in a second fixed position, and is configured to acquire the image beam so produced. The component under inspection and the line scan camera are both stationary during the scanning interval, thereby reducing or eliminating one or more of the problems as set forth in the Background.
In a preferred embodiment, the optics comprise a first mirror, and a scanning mirror. The first mirror is moveable between a first position and a second position, while the scanning mirror is moveable from a first start orientation to a first stop orientation. The first mirror, which may be a pivoting mirror, when in the first position, is configured to direct the source light beam to the scanning mirror by way of a first stationary mirror. The scanning mirror is configured to scan a portion of the ID surface using the source light beam when moving from the first start orientation to the first stop orientation.
In a still further preferred embodiment, the scanning mirror further includes a respective second start and stop orientation. The first mirror, when in the second position, is configured to direct the source light beam to the scanning mirror by way of a second stationary mirror. The scanning mirror is configured to scan the remainder of the ID surface of the component under inspection when moving from the second start orientation to the second stop orientation. In a constructed embodiment, the area of the ID surface scanned by the scanning mirror by way of the first stationary mirror is about one-half the total area, while that scanned by the scanning mirror by way of the second stationary mirror comprises the other half.
A method for inspecting a component is also presented.